An asteroid the size of my front yard will zoom by 59,650 miles from, well, my front yard tonight. At average walking speed, you could step from one end of this boulder to the other in just 13 seconds.
2012 TC4 was discovered on October 4 with the 1.8-meter telescope at Haleakala Observatory in Hawaii as part of the Pan-STARRS survey to discover and characterize Earth-approaching comets and asteroids that might become a hazard to the planet.
No one’s in danger from this midget asteroid because it’s much too far away to trouble the lumbering Earth. If anything, our planet’s gravity will likely bend and alter 2012 TC4’s path during closest approach. That happens at 12:31 a.m. (CDT) tomorrow morning Oct. 12.
Amateur and professional astronomers have been studying the asteroid’s light variations since discovery and determined that it rotates very quickly, perhaps as fast as one spin every 12 minutes. Its brightness also varies by about 1 magnitude during a rotation. These are good things to keep in mind if you’re considering tracking it tonight.
You’ll need at least a 10-inch telescope and haze-free skies to find this hasty rock. Not only will it be moving quickly in front of the stars but at brightest will shine only between 13.6-14.0 magnitude. That’s over 1500 times fainter than the faintest star most of us can see with the unaided eye. Around the time of closest approach, 2012 TC4 will be peeling through the stars of Sagittarius at approximately one degree (two full moon diameters) every 5 minutes. If you can catch up with our little friend, you’ll see it cross the telescopic field of view in real time just like a man-made satellite.
Tracking something that fast and faint requires making your own maps using star charting, planetarium-style programs like SkyMap, MegaStar, Cartes du Ciel (free) or a scope with automatic pointing ability. These programs have the option of adding an asteroid and its orbital elements to the database. With that information, you can print your own chart showing its path. Click HERE for 2012 TC4’s orbital elements for manual input or HERE to download them right into your program.
If that fails, you can hand-plot its position on a star atlas. Since 2012 TC4 will be so close to Earth, different locations will see the asteroid take slightly different paths across the sky, this might be the best option. To find the path for your location, you’ll need to go to JPL’s HORIZONS Web-Interface site, change the observer location line, select your time span and then click the Generate ephemeris button for a table of positions of the asteroid for every minute, every hour, etc. Remember that the times shown in the table are Universal Time (UT). Subtract 4 hours for Eastern Daylight, 5 for Central, 6 for Mountain and 7 Pacific.
If all this asteroid talk is bit much, how about something brighter and easier to see? Luckily, we have just the thing tomorrow morning October 12 at dawn, when the crescent moon will shine near the planet Venus. Nice to know there’s something for everybody out there.